add org-version function for elfeed compatibility

[Luis-Henriquez-Perez]

Hi
I've used your hack for overriding emacs's tendency to use its built in org-mode instead of the latest release. It works pretty well. One thing I found though is that an error comes about with the Elfeed emacs package because it used the function (org-version) in its elfeed-link.el file. org-version returns "N/A" with the hack. Elfeed expects a string that can convert it to a number. (version< (org-version) "9.0").
This is easily fixed with a (defun org-version () "9.1.3"). Just wanted to recommend this in case you or anyone who used this hacks uses packages like elfeed that call (org-version).

[raxod502]

This will be fixed (by virtue of the hack no longer being necessary) when radian-software/straight.el#72 and radian-software/straight.el#115 are closed. Thanks for the report. I'm happy to accept a pull request patching Radian in the meantime.